Electrical measuring instrument.



L. W. CHUBB.

ELECTRICAL MEASURING INSTRUMENT.

APPLICATION FILED APR. I0. 1911.

1,1121 1. Patented May2,1916.

I @FFIQE.

LEWIS W. CHUBB, or nnenwoon PARK, PENNSYLVANIA, ASSIGNOR TO WESTING-HOUSE ELECTRIC AND MANUFACTURING COMPANY, A CORPORATION or PENNSYL-VANIA.

T 0 all w/wm'z't mag concern:

Be it known that I, LEWIS W. CHUBB, acitizen of the United States,andraresident. of =Edgewood Park, in the county of Allegheny. and Stateof Pennsylvania, have in vented a new and useful Improvement inElectrical Measuring Instruments, of which the folltnvingis aspecification.

My invention relates to electrical measuring instruments, and it has forits object toprovide' an instrument of the above-indicated class thatshall be simple, compact and-durable in construction, accurate andreliable in operation, and be particularly adapted ,to indicate theaverage or arithmetic mean of the instantaneous values of an alternatingelectro-motive force wave of a given frequency.

Heretofore, electrical measuring instruments which have been employedfor indicating the voltages of alternating current sources of. energyhave been so constructed as to register thesquare-root-of-the-meansquare value of the instantaneous voltages.However, recent developments in the electrical art have made itdesirable to produce an instrument which is adapted to measure averagevalues of voltage waves, without regard to sign, in order thatdeterminations of the, form factor thereof may be readily made. Aknowledge of the form factor of electromotive force waves isparticularly desirable in some classes of electrical testing work, andin the design and construction of electrical apparatus to be used tosupply certain types of systems. 7

Formerly, the determination of the form factor of a voltage wave hasbeen accomplished through the agency of an oscillograph or a synchronouscommutator, but such determinations involved very delicate and expensiveapparatus and necessitated more or less complicated calculations. Hencethe importance of a simple device whereby the form factor is easilydetermined.

Inasmuch as the form factor of a voltage Specification ofLettersPa'tent.

' Patented May 2, 1916.

Application filed April 10, 1911. Serial No. 620,171.

apparatus is composed of a loss due to eddy currents and a loss due tohysteresis. Moreover, the eddy current loss is dependent upon thesquare-root-of-the-mean-square value of the impressed electromotiveforce, while the hysteresis loss is dependent upon the maximum value ofmagnetic induction in the iron which, in turn, is dependent upon theaverage of the instantaneous values of the impressed electromotiveforce.

According to my invention, I provide an instrument which is based uponthe principle just recited and which consists of an iron coreconstructed of extremely thin laminations of magnetic material andpractically free from eddy currents, and the hysteresis of which isindependent of the wave form of the voltage impressed upon its windings.For convenience, I term such a core aneddyless core, by which I meanthat no eddy currents are set up therein when voltage is supplied to itsWinding. Hence, the eddy current losses are eliminated andthe core lossconsists entirely of hysteretic losses.

The above mentioned core is employed in connection with a suitable metermechanism which will measure energy input to the core and which hascompensating coils to subtract or neutralize any torque due to copperlosses in its own windings, which torque would be dependent upon thesquareroot-of-the-mean-square value of thevoltage. Since the iron corehas no eddy cur rents and, since the meter mechanism does not registerany copper losses, which are dependent upon thesquare-root-of-themeanesquare values of electromotive force. it isevident that the deflection or torque of the instrument will be entirelydependent upon the hysteresis loss in the core and will be a function ofthe maximum magnetic induction which is, in turn, proportional to thearea of the impressed voltagewave or to the average value thereof.

My invention may best beunderstood by reference to the accompanyingdrawing, the single figure of which is a diagrammatic view of thecircuit connections and arrangement of parts of an electrical measuringinstrument which embodies my invention.

Referring to the drawing in detail. the device herein shown comprises amagnetizable.

core member 1 havinga winding 2, and a meter mechanism 3 which comprisesstationary windings l and 5, a movable coil or winding (5 disposed inelectro-magnetic relation thereto, an indicator or pointer T attached tothe coil 6 and adapted to traverse a suitable scale 8, a spiral spring 9to oppose the torque of the coil (3, a non-inductive resistance l0 andcompensating coils 11 and 12 for a purpose to be hereinafter set forth.

The magnetizable core member 1 is so con" structed as to be free fromeddy currents when voltage is impressed upon its winding 2,this being anessential feature of my invention. Such a core may be conveniently madefrom a plurality of extremely thin laminations of magnetizable materialor, in some cases, it may be expedient to build it of alternate layersof very thin paper and extremely thin laminations.

I desire it to be understood that the core member 1 is not restricted inany way to the structural details just mentioned, as any core memberwhich is so constructed as to pre vent the development of eddy currents,may be employed for the same purpose.

Th stationary windings 4 and 5 constitute the series coils of theinstrument and are connected in series with the winding 2 of themagnetizable eddyless core member 1, while the movable winding or coil 6is connected in shuntthereto through the non-inductive resistance 10,and the compensating windings 11 and 12. The lead 13 of the compensatingwinding 11 is connected to conductor 14: between the series coil 4 andthe winding 2, and the lead 15 of the resistance 10 is connected toconductor 16 adjacent to one of the terminals 17 of the instrument.Thus, it is evident that the compensating windings 11 and 12, themovable coil 6 and the resistance 10 are connected directly across thewinding 2 of the eddyless magnetizable core 1 and the current therein istherefore affected by the potential drop across said winding, while theseries coils 1 and 5 are connected on the line side of this shuntcircuit.

It is well known that the deflection of an instrument which is affectedby the copper losses in its own windings is influenced by thesquare-root-of-the-mean-square value of the impressed voltage, and,therefore, inasmuch as the instrument of my invention is to be adaptedto indicate average values, it becomes necessary to exclude the effectof these copper losses.

It has been pointed out that the extremity of the compensating coils 11and 12 is connected to conductor 14 between the series 0011 4 and thewinding 2 and, hence, the deflection of the instrument is independent ofthe copper losses in said series coils.

In order to annul or compensate for the effect of the copper losses inthe shunt circuit, I provide the compensating coils l1 and 12 with thesame number of turns as the series coils l and 5 and connect the same inopposition to the series coils whereby the influence of the copperlosses in the shunt coil (5. the compensating coils 11 and 12 and theresistance 10 is subtracted or eliminated.

It will be understood that the instrument is essentially a wattmeter,the shunt circuit, including the movable coil (3, being adaptedto-mcasure the drop across the winding 2, while the series circuit,including the series coils 1 and 5, is traversed by the current passingthrough the winding 2 plus that traversing the movable coil 6. However,by connecting the compensating coils in the manner hereinbeforedescribed, the influence of the series coils, by reason of the currentwhich traverses the shunt circuit, is neutralized and, hence, theinstrument measures only the power consumed in the magnetizable coremember 1.

Inasmuch as the core member 1 is so con structed as to be free from eddycurrents, it is evident that the power expended therein depends upon themaximum induction in the iron which is proportional to the area of theimpressed voltage wave or to the average value thereof. Thus, if thescale 8 be cali brated to read the average volts of a given circuit, itwill read the average volts of any circuit of the same normal frequencyto which it may be connected. v

I have illustrated my invention as embodying an instrument of aparticular type, but it should be understood that my invention is notrestricted in this respect. Furthermore, modifications in thearrangement of parts and circuit connections may be effected withoutdeparting from the spirit and scope of my invention and such variationsare intended to be covered by the appended claims. v

I claim as my invention:

1. A voltage-indicating instrument comprising a laminated magnetizablecore member subject to hysteretic losses only, a wind ing permanentlydisposed thereon, and a wattmeter mechanism adapted to measure thelosses in said core member.

An electrical instrument for indicating average values of an alternatingcurrent voltage wave comprising an eddyless magnetizable core member, awinding therefor, and a powermeasuring mechanism calibrated in volts tomeasure the energy consumed in said core member.

A voltage-indicating instrument comprising an eddyless magnetizable coremember, a winding therefor, and electrical means for indicating thearithmetic average of the instantaneous values of an electromotive forcewave impressed on said winding.

4. A voltage-indicating instrument comprising a laminated magnetizablecore member subject to hysteretic losses only, a winding therefor and awattmeter mechanism calibrated in volts for measuring the losses in thesaid core member.

5. In an instrument for'indicating average voltage Values of analternating current wave, the combination with a consuming devicecomprising a core member, and a winding therefor, of means associatedtherewith that is calibrated in volts and dependent upon the maximummagnetic induction in said core member for measuring the energy consumedtherein.

6. An instrument for indicating average values of an alternating-currentvoltage Wave comprising an eddyless magnetizable core member, a windingpermanently disposed thereon and a wattmeter calibrated in volts soconnected as to measure the energy consumed in the said core member.

7 An instrument for indicating the average value of analternating-current voltage wave comprising an eddyless magnetizablecore member, a winding therefor and a wattmeter calibrated in volts formeasuring the energy consumed in the said core member when the windinghas impressed thereon an alternating-current voltage.

8. An electrical: instrument :lEor mdicating average values of analternating-current voltage wave comprising an eddyless magnetizablecore member, a winding therefor and a compensated power-measuringinstrument calibrated in volts for measuring the ener consumedin thesaid core member.

9. n electrical instrument for indicating average values of analternating-current voltage wave comprising an eddyless magnetizablecore member, a winding therefor Lnw s w. oHU B.

Witnesses: v

B. B. Hmns, M. C. Mnnz.

